Sand Filter or Cartridge

by Robert
(Seminole, FL USA)

I recently just purchased a home and am a first time pool owner. I have a sand filter that is acting up the pool is 22000 gallons. I have back washed the filter and made sure water was clean before turning it back to filter. I have spots in my pool it looks like black algae. I test the chemicals weekly and everything is good but it still will not go away. My sand filter now is causing bubbling in my pool and I had to shut my pump off, it was burning.

How do u recommend I go with a cartridge system and what kind for a 22 thousand gallon pool and how do i get rid of the black algae? My water is blue but the spot look black at the bottom and I brush them they go away next day there back.

Thanks for the question Robert

I would recommend going with a cartridge filter. The filtering efficiency rates between a DE, which is the best but most troublesome, and sand. Simply takes the filter out, spray it out and reinstall it.

Bubbles in your pool is normally a return side issue. You have the suction side which goes from the pool's skimmer and bottom drain to the pump motor. Everything after that is the return side. I have a couple of videos on YouTube on troubleshooting this very issue. Go to YouTube and the channel name is clean Pool and Spa. It goes much faster and it's more detailed than writing it.

Sizing a cartridge filter is pretty easy. My general rule is for every 10k gallons you want 200 sq. ft so a 20k gallon pool would need about 300 - 400 sq. ft. You can go a bit oversize on the filter but not the pump motor. A 1 HP pool pump for 20k gallons is good. You want 1 full turnover of the water. This means that all of the water gets filtered and this normally takes about 8 - 10 hours.

Once you have black algae you can only contain it. Black algae has layers and tentacles and digs down into the plaster. You need to scrape the top of it off then scrub the affected area with a chlorine tab. You can use a product called Algae Gon Chlorine Tablet Holder.

Once this is finished you can apply a thin layer of Dichlor or Trichlor chlorine to the steps and bottom, the best you can. Be careful with these products because they have stabilizer in them and will raise the CYA.

Shock the pool with liquid chlorine. It's 2 gallons to increase the chlorine level to 10ppm per 20k gallons. You can use 2.5 gallons to reach about 11ppm. FILTER for 24 hours then take a look at any more possible affected areas.

I'm also in Florida not too far from you. If you want we can exchange numbers and I can talk you through a few more things that new pool owners need to know. Hope this helps.


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Vacuuming With A Cartridge Filter

by Reen
(Sydney, Australia)

My inground pool has a cyclone cartridge filter system. There are 3 valves: one attached to the cartridge housing, one to the pool pump and one for the purging of the cyclone chamber. Each valve only has 2 options - shut or open. I have tried vacuuming the pool a number of times and the following day there is a fine layer of dust/dirt in the bottom of the pool. I have cleaned the cartridge filter, emptied both skimmer boxes (pool and pump) and have purged the cyclone chamber. I have tried vacuuming without the cartridge, with the cartridge;

I have vacuumed with cartridge housing and pump housing open (filter mode) and have tried it with them closed and the purge line open (high loss of water that is attached to my storm water). The water is blue and clear and has the correct ph levels. I had used some clarifier previously and it has the correct chlorine and acid levels. Any suggestions?

Thanks for the question Reen

The MultiCylone filter is pretty new on the market. I have not had the opportunity to examine it first-hand but I am intrigued by it. It was very interesting that you posted a question.

Dirt going back into the pool is usually a return side issue. This is from the pump motor through the filter and back into the pool. You have 2 layers of filtration now, the cyclone and the cartridge filter. There are 3 possible scenarios, or perhaps a combination. First is the cyclone is somehow compromised. It may have a hole or crack which is allowing dirt to flow through.

2nd is the cartridge filter. They only last about 2000 - 2500 filter hours. After that the pleats become too thin to properly capture dirt. It may also have small holes that's allowing dirt to pass through. If your filter is too old it may need to be replaced.

Last is a possible leak on the return side. The dirt is getting into the plumbing and going back into the pool through the returns.

Any dirt that is being vacuumed should either be captured by the cyclone and/or the filter. Dirt is going back into the pool so I'd start with the above and see what you can find.


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